How reliable is forensic bite mark analysis? Everyone knows that a bite mark on Lisa Levy ended Ted Bundy's crime spree, but many convictions are now getting overturned.

Teeth are Used as Weapons

Human bite marks are found when teeth are used as weapons - weapons of anger; weapons of passion; weapons of control or weapons of destruction.

It is relatively simple to record the evidence from the bite mark injuries and match the teeth for comparison of the shapes, sizes and pattern that are present, but the science is not as exact as other forensic sciences and there is a lot of contoversy about the accuracy of bite mark evidence.

Skin is elastic and distortable which makes forensic bite mark analysis complicated; and the human jaw grows and changes over time which makes teeth marks left by a suspect a few years before, not always easy to match accurately to his/her teeth. However, often saliva is found on bite marks which can assist law enforcement with DNA profiles for identification

Most Famous Bite Mark Conviction – Ted Bundy

Probably, the most famous incident where human bite mark evidence led to a conviction, was the case of the notorious serial killer, Ted Bundy. Nobody really knows how many people Bundy killed between 1973 and 1978, but he was finally tied to the murder of Lisa Levy who he attacked in the Chi Omega Sorority house at Tallahassee's Florida State University, through bites that he inflicted on her body. Forensic bite mark analysis revealed Bundy’s highly irregular teeth left the impressions.

Typical Presentation of Bite Marks

Human bite marks are most often found on the skin of victims. Women are most often bitten on the breasts, buttocks and legs during sexual attacks, whereas bites on men are commonly seen on the arms and shoulders.

How Bite Marks are Recognized

• Often the differences in size and shape of teeth are very obvious to even a layman, for instance when someone has teeth missing or very prominent teeth.
• A representative human bite mark is described as an elliptical or circular injury that records the specific characteristics of the teeth.
• According to an article in the British Dental Journal by Drs David Sweet and Iain Pretty, the sizes, shapes and pattern of the biting edges of the anterior teeth that are arranged in the upper and lower dental arcades are thought to be specific to that individual. This is mainly caused by the sequence of eruption of anterior and posterior teeth.
• Bite marks with high evidentiary value that can be used in comparisons with the suspects' teeth will include marks from specific teeth that accurately record distinct traits. It is possible to identify specific types of teeth by their class characteristics.

Details of Evidence Collection Techniques

Often the bite marks are clear but other times they are faint or even not visible to the naked eye and are only picked up when the Ultraviolet (UV) light detects saliva. A saliva sample can be taken from the bite from which DNA analysis and blood typing can be done.

Then linear scales, one for width and one for height, are placed near the mark and the bite marks or suspected bite marks are photographed.

Forensic Bite Mark Analysis

Accurate casts of the teeth must be produced. These casts can be made from a variety of materials like silicon rubber, plastic and powders.

In the case of a deceased person, the bite mark be excised for further forensic bite mark analysis or the whole body may be taken to a facility where it will be examined.

With this type of information and with the benefit of computerized bite analysis software, a highly detailed picture of the bite mark can be developed.

Once teeth impressions are taken from a suspect these can be compared against the bite mark data and matched for up to seventy-six comparison factors. These include whorls, indentations, chips, abrasions, striations, distances between cuspids, tooth width and thickness, alignment and mouth arch.

Bite Mark Evidence Controversy

According to New York Times Article (28.1.2007) Evidence From Bite Marks, It Turns Out, Is Not So Elementary the CSI Effect has exaggerated the effectiveness of bite mark evidence. A 1999 study by a member of the American Board of Forensic Odontology, a professional trade organization, found a 63 percent rate of false identifications. Many bite mark cases get overturned.

“If you say that this bite fits this person and nobody else in the world, and if you use the bite mark as the only piece of physical evidence linking an attacker to his victim, that’s not science — that’s junk,” said Dr. Richard Souviron, chief forensic odontologist at the Miami-Dade Medical Examiner’s Office.

Bite marks, however, can be helpful in excluding someone as a suspect, or determining that the suspect could be the one who inflicted the bite, many experts and defense lawyers agree.

Sources:

Forensic Dentistry Online